Authors:
Samantha Vanderslott, Hana Rohan
Corporate Author:
Social Science in Humanitarian Action Platform
Published:
2025

This brief provides an overview of the experimental stages of vaccine development during a disease outbreak and highlights key considerations at each stage from a social science perspective. This brief complements a recent SSHAP publication that synthesised social and behavioural science (SBS) evidence on vaccine trials in health emergencies. This brief outlines designs and approaches to introducing experimental vaccines during health emergencies. It then presents the SBS and risk communication and community engagement (RCCE) dimensions to consider with the introduction of experimental vaccines. The final section presents an overview of the use of experimental vaccines in recent health emergencies – including Ebola virus disease (EVD) and COVID-19 – and the associated SBS and RCCE considerations.

This brief will be useful to humanitarian workers, social scientists, policymakers and people responsible for designing research or providing guidance during health emergencies, including scientists and communications specialists. The brief is based on a rapid review of published academic and grey literature, media reports and professional experience.

Key considerations

  • Engage and communicate with the wider public and specific groups about experimental vaccine introduction during disease outbreaks. Use social and behavioural science (SBS) and risk communication and community engagement (RCCE) to provide insights from research, ethics, roll-out and vaccine implementation as epidemiological conditions change. Clear communication and engagement will help to strengthen and maintain confidence in local public health authorities.
  • Design communications strategies that are informed by rapid formative SBS research. Insight gathered on perceptions of vaccines with potential participants and the wider community – and which draws on best practice – can help inform messages that are more likely to result in a positive perception of vaccines.
  • Establish and use patient and public involvement and engagement groups as part of the process for trials of experimental vaccines seeking regulatory approval. These groups can integrate participant/community perspectives across multiple areas and feed into ethics on informed consent, reimbursement, specific procedures and recruitment.
  • Conduct stakeholder power mapping to reconcile competing interests for how benefits and risks are shared. Stakeholder power mapping can identify trusted and influential authorities or highlight gender and power dynamics that might affect or be affected by the use of an experimental vaccine in a trial or outside of a trial setting.
  • Encourage dialogue about potential ethical concerns by involving the community in vaccine research and the introduction of experimental vaccines. The introduction of an experimental vaccine raises a number of ethical concerns (e.g., informed consent). Community views are needed to avoid the exploitation of vulnerable populations, maximising the benefits of vaccine trials while reducing risks and burdens.
  • Plan for RCCE specialists to lead community dialogue and situation monitoring. A changing epidemiological situation will require ongoing dialogue and monitoring by appropriate specialists to identify accepted channels of communication and monitor community perspectives.
  • Align communication and engagement strategies with local priorities. It is critical to develop tailored messaging and framing, especially towards influential groups (e.g., healthcare workers) and vulnerable groups (e.g., children and pregnant women), and to adapt messaging depending on vaccination status. The impact on local health systems, services and research should also be considered.
  • Increase confidence through consistent and clear messaging and stop the spread of misinformation by engaging with communities.Changes in messaging can often be a part of a dynamic trial process and epidemiological situation, but can lead to public confusion and declining confidence in public authorities’ ability to manage a crisis. Communities may become hesitant to participate in trials if they feel excluded from the decision-making process or distrust the implementing teams involved. This hesitancy can lead to low enrolment rates and hinder the development of effective vaccines.
  • Encourage vaccine uptake through continued community engagement strategies. It is important to continue engaging with communities after a vaccine has been developed: there is a positive association between engagement and uptake of vaccines.

Context

The introduction of experimental vaccines during disease outbreaks and other health emergencies has historically been approached with caution, largely due to ethical and logistical challenges. However, in recent years the introduction of experimental vaccines has often become a central component of outbreak response strategies.1 An experimental vaccine (sometimes called ‘investigational’) is a previously untested vaccine that is introduced to human subjects, either as part of a clinical trial or outside of a trial, after basic laboratory experiments.

The roll-out of experimental vaccines has largely focused on the scientific-technical and operational challenges of trials. These efforts to prepare vaccines for roll-out – which typically involve manufacturing, scaling up, ensuring sufficient supplies and related infrastructure, and resources – are essential to managing disease outbreaks. While research teams have committed substantial effort to trial design methodologies, as well as ethical dimensions around trials, there has been an insufficient focus from trialists on the social dimensions associated with experimental vaccine introduction during emergencies.

Engaging the public appropriately during disease outbreaks is critical to ensuring that decisions about the use of experimental vaccines consider people’s concerns and feedback. There are many examples (e.g., during the COVID-19 pandemic) where decision-making processes did not adequately engage the public or reflect their views. This insufficient engagement resulted in several outcomes that damaged the overall epidemic response and hindered vaccine uptake, including reduced trust, increased misinformation, heightened ethical concerns, and inequitable access to public health measures.

There are numerous experimental vaccines in development that might see potential introductions during disease outbreaks. Marburg virus disease and Lassa fever, for example, are considered to have outbreak potential but do not currently have vaccines licensed for human use. Both diseases are therefore included in the World Health Organization (WHO) research and development blueprint of priority pathogens for which there is an urgent need for accelerated research and development.2 There are vaccine candidates undergoing later stage trials: a Marburg virus disease vaccine trial is being conducted in Uganda and Kenya;3 and a Lassa fever vaccine trial is underway in Nigeria, Ghana and Liberia.3,4 Experimental vaccines are becoming a common feature of emergency response, and there is a pipeline of candidates stemming from policy prioritisation, such as the WHO Research and Development Blueprint for Epidemics.5

Approaches to introducing experimental vaccines

There is a standard pipeline process of testing vaccines via clinical trials. This typically starts with safety and immunogenicity tests on smaller groups of people before the tests are expanded to a larger population in a clinical trial. Testing in human populations is usually needed to establish the safety and efficacy of a new vaccine. An existing vaccine may also be tested to establish the dose, combination of vaccines, route of administration or application to a new disease or condition.6

There is a process to use experimental vaccines for emergency use. In some instances, a new vaccine may be used (or an existing vaccine repurposed) without undergoing a clinical trial, although a degree of regulatory and ethical approval will always be required. Regulatory and ethical approval outside of a trial includes approval for compassionate or expanded access.

Previously, there have been three common regulatory pathways that countries have taken for the authorisation of vaccine use outside of trials.7 The first allows authorisation via compassionate use or expanded access – even where limited clinical data are available outside a trial – if it is determined that the potential benefits outweigh the risks in the face of a life-threating condition. The second is increased interaction between regulators and sponsors to help conduct a more rapid review of the vaccine. The third pathway has shortened regulatory review timelines for assessment and evaluation by providing additional resources (e.g., personnel). Today the WHO recommends that the ‘monitored emergency use of unregistered and experimental interventions framework’ (MEURI framework) be used in place of ‘compassionate use’ or ‘expanded access’ with the intention of allowing patient access to health interventions as quickly as possible to counter disease threats.8

In recent disease outbreaks, experimental vaccines have been tested using randomised controlled trials (RCTs) and human challenge studies. The RCTs, which may randomise clusters (cluster RCTs), have tested experimental vaccines using ring vaccination and post-exposure vaccination/prophylaxis, for example. Both ring vaccination and post-exposure vaccination/prophylaxis may also be used outside of trial settings. The approach taken may be specific to the outbreak and the context of the changing epidemiological situation.

Each approach and study design has unique social and ethical implications that need to be considered. It has also been noted in a report from the National Academies of Sciences, Engineering, and Medicine that the research setting of a trial means that autonomous healthcare decision-making can be challenged by the need to adhere to standardised protocols, which are controlled through processes such as randomisation, rather than relying primarily on interactions between health professionals and patients.9

Cluster RCTs

In cluster RCTs, groups or ‘clusters’ (rather than individuals) are randomly allocated to treatment or control arms; for example, these can be geographic clusters. The SMART trial for mpox described in Box 1 is a cluster RCT targeting household members of mpox patients in defined geographic areas.

Cluster RCTs are suited to epidemic situations where individual randomisation to treatment arms is not possible, where it is more appropriate to deliver an intervention to a whole cluster (e.g., a village or school) than to individuals, or where it is difficult to assess individual outcomes (e.g., it can be more costly and time consuming to follow up with individuals).10

The parameters for inclusion criteria for groups can pose a challenge in how to engage the population that is being targeted as well as how to explain exclusion to those not included in a trial.

Ring vaccination

For ring vaccination, confirmed cases and their contacts form a ‘ring’, and these rings are randomised to either be vaccinated as part of a cluster RCT, or with individual randomisation inside rings.11

Ring vaccination was first used in the 1970s for smallpox before it was declared eradicated in 1980. It focuses on vaccinating those people with the highest risk of contracting a virus. This approach is suited to an epidemic situation where the spread of a pathogen is highly focused and unpredictable.12

Ring vaccination was next used during the 2014 to 2016 West African EVD epidemic.12 Challenges associated with this trial design for EVD included issues with the identification of close contacts and the best approach for communicating information about who was included or excluded from the trial, and why.13 Social scientists have urged that community engagement efforts during trials should be expanded to focus on the wider population, and not just target groups and potential participants. They have also emphasised the importance of engaging with populations with specific vulnerabilities who may be under-served or viewed as more difficult to engage with, such as rural populations or those with limited literacy.13

Post-exposure vaccination/prophylaxis

In post-exposure vaccination/prophylaxis, vaccination is given after suspected exposure to modify or prevent disease among those who may have already been infected. The effectiveness depends on factors such as individual immune responses and population-level spread of the disease. Post-exposure vaccination/prophylaxis has been used for diseases such as rabies and smallpox.14 Experience from rabies post-exposure vaccination/prophylaxis has underscored the need for awareness-raising to increase understanding of the need to vaccinate after suspected exposure.15

Vaccination before exposure to a disease (pre-exposure vaccination) has typically been the main approach to communicable disease control, and, as a result, post-exposure vaccination can be less well understood by the public. Rabies and smallpox are exceptions in that both vaccines had been shown to have near total efficacy in exposed individuals when administered post-exposure and therefore that post-exposure vaccination is an effective approach for disease control.

In the ongoing mpox epidemic in Central and Eastern Africa, the WHO has recommended targeted vaccination for mpox, including post-exposure vaccination/prophylaxis.16 Even though a pre-exposure vaccine has been licensed, trials for the use of the vaccine for post-exposure vaccination/prophylaxis are still required. These trials will provide more data on the effect of post-exposure vaccination on the severity of illness and length of symptoms.

Practitioners involved in SBS and RCCE must consider how to best explain that post-exposure vaccination/prophylaxis for certain diseases can be effective even after suspected infection, and that it can help counter the spread of disease and protect others.

Human challenge studies

In human challenge studies, researchers deliberately expose healthy volunteers to pathogens to monitor how the body responds to the disease and to test the efficacy of new vaccines. Human challenge studies may be used to assist the development of future vaccines during a disease outbreak. These studies can be advantageous because of their speed and efficiency.

However, human challenge studies have also been subject to ethical controversy. For example, in the past, vulnerable groups, such as prisoners and racially and economically marginalised groups, have been purposively recruited as human challenge study participants.17 Today, ethicists maintain diverse views on when human challenge studies are acceptable, depending on the disease and context. Qualitative research has emphasised the need to clearly communicate the risks and benefits of participation, ensure informed consent and consider local decision-making structures.18

The WHO published guidelines on the ethical acceptability of COVID-19 human challenge studies.19 Human challenge studies took place after vaccines had been developed, and these studies appear to have adhered to the scientific and ethical assessment criteria set out by the WHO.20

Considerations for introducing experimental vaccines

There are SBS and RCCE dimensions to consider at each stage of introducing an experimental vaccine, including during the design and planning of trials, seeking research and ethical approval, and the testing and collection of data during trials or the roll-out of experimental vaccines outside of trial settings.

There have been significant calls to improve the integration of participant and community perspectives in trial design and implementation since the West African EVD outbreak in 2014.21 Integration of SBS and RCCE is increasingly seen as critical. Those designing trials or overseeing experimental vaccine introductions should consider how best to engage with communities about an experimental vaccine roll-out as well as how communication and community engagement approaches may need to change due to the rapid pace and uncertainty typically encountered during health emergencies.

For example, equity concerns may arise when there are limited doses available for distribution; or communication strategies may need to change when a trial is no longer possible due to declining cases or if a trial is complicated by an outbreak of another disease in the same geography (e.g., COVID-19 and EVD in the Democratic Republic of Congo in 2021; mpox and Marburg virus disease in Rwanda in 2024).

Researchers have emphasised that ethical research should involve communities to address health inequalities and should also consider community facilitators and facilitating organisations.22 Improved access to information about vaccine trials and the use of vaccines outside of trial settings can mean communities are more likely to benefit from the development of new vaccines, especially in terms of increased acceptability and uptake through the representation of marginalised voices or experiences.23

Further, without proper engagement, communities may be more susceptible to misinformation and conspiracy theories about vaccines. Misinformation and conspiracy theories can erode trust and discourage participation in trials or eventual vaccine uptake. It is important to include the voices of underrepresented community members and to communicate openly when an error has been made by rapidly issuing correct information.

Even where a vaccine is successfully developed and appropriately trialled, lack of community engagement can lead to low uptake rates, which can hinder efforts to control the disease outbreak. Some studies have shown how individuals from underrepresented communities can be susceptible to misinformation,24 whilst others have shown a positive association between community engagement and vaccination rates.25 Engagement should align with relevant local knowledge (e.g., about illness, health-seeking behaviours) and use locally spoken languages and culturally sensitive approaches.25

Introducing an experimental vaccine as part of a clinical trial or outside of a trial setting

Deciding whether or to what extent to conduct a trial of an experimental vaccine in a health emergency often involves a trade-off between managing the disease outbreak and collecting information for later use (to allow for vaccine approval and potentially better options to protect populations in the future).9 Consensus has not been reached about whether providing clinical care and conducting clinical research must be mutually exclusive – while there can sometimes be obvious tensions, this can also be addressed by adapting study designs.

Further, conducting a trial might be deemed appropriate for one medical intervention but not another. Whilst the Marburg virus disease vaccine was not introduced as part of a trial in Rwanda, the WHO with the Government of Rwanda and partners are conducting a RCT to test the efficacy of Marburg virus disease treatments (the antiviral drug remdesivir and a monoclonal antibody).

Regulation in emergencies

Outbreaks require adaptation of conventional systems of medical regulation and governance. ‘Emergency use’ is a regulatory mechanism to facilitate the availability and use of medical countermeasures, including vaccines, during public health emergencies.26 These are often temporary mechanisms and, for vaccines, are applied when a vaccine is not yet approved in a country. ‘Emergency use’ allows vaccines to be used ‘off-label’ for different circumstances in disease outbreak settings where the benefits of vaccination outweigh the potential risks.

During an outbreak, for example, people of certain ages (usually infants, children and adolescents) and vulnerable people (pregnant or breastfeeding, immunocompromised) could be provided with the vaccine even if the safety and immunogenicity for these groups have not necessarily been demonstrated through trials.

During the COVID-19 pandemic, countries revisited the provisions and procedures for the emergency authorisation of pharmaceutical products. Observations and comparisons were made for speed and how fit-for-purpose the provisions and procedures were, alongside pressure to make some experimental products available. A report by the WHO and the International Coalition of Medicines Regulatory Authorities found that some countries were able to use existing regulatory frameworks, but other countries needed to develop interim measures quickly.27

Even though regulatory approval for emergency use of vaccines is still required, there has been a widespread public perception that regulation during a disease outbreak is overlooked or that approvals are rushed or less stringent. This can affect perceptions of how safe vaccines are, despite there being little evidence that safety is affected.28

Responses to a changing epidemiological situation

The epidemiological situation has implications for how to alter communications and community engagement strategies during trials. For example, a reduction in the number of cases of the disease being investigated can affect the ability to conduct trials to measure efficacy. Public health and social measures intended to suppress transmission can slow down or fundamentally impinge trial progress because there are not enough cases; this was an issue during the various COVID-19 waves, for example.

Ethics of selecting groups to receive the experimental vaccine

Studies that are conducted unethically can damage trust and can have a negative impact on future trial participation and uptake of pharmaceutical interventions. The tension between controlling disease outbreaks and testing vaccines forms the backdrop to many of ethical and social debates.

The increased resources and funding that are channelled towards an outbreak can also fuel scepticism about the intentions of researchers. However, the need to conduct research and collect data is crucial for not only controlling current outbreaks but also for future pandemic preparedness. Data can first be collected on safety and immune response, and efficacy can be assessed across multiple outbreaks. These safety and immunity aspects can also be measured via trials that do not need to follow the gold-standard RCT trial design.

Effectiveness can be shown after a vaccine is approved, by seeing how well vaccines work in the real world in larger populations. Therefore, there are expanding possibilities to collect data and conduct research outside of RCTs, but these different approaches continue to require the consideration of ethical and social dimensions.

The Tuskegee Syphilis Study and zidovudine (AZT) trials in Zimbabwe are examples of unethical therapeutics studies conducted on vulnerable groups that have damaged trust.29 The Tuskegee Syphilis Study of African-American men (1932 to 1972) was an infamous study conducted by the U.S. Public Health Service, where men with late-stage syphilis and controls without the disease were observed but not treated, despite the availability of treatment.30 The AZT trials in Zimbabwe in the 1990s were studies conducted by U.S. doctors and the University of Zimbabwe without proper informed consent, with control groups given a placebo rather than an effective drug (to prevent HIV transmission from pregnant women to their babies).31

A critical ethical question arises around the need to balance the risk of infection or severity of the disease with the risk of an experimental vaccine. For example, during recent Ebola virus disease outbreaks, an ethical question arose around the provision of the experimental Merck vaccine (rVSV-ZEBOV) to pregnant and lactating women and in children under one year of age, as these groups were excluded from earlier trials and then included in later trials.32

When such questions arise it is often those directly implicated (i.e., in this case, pregnant and lactating women) who are not consulted and who are notably absent from making decisions for themselves about the risks and benefits associated with experimental vaccines. Qualitative data collected by UNICEF in Beni highlighted children were high risk and not routinely vaccinated, and interviews with pregnant women showed how they were dissatisfied with their exclusion.32

Some ethicists have argued that the MEURI framework is impractical (because it is a complex, rigorous and principled framework that overlaps with standard research practices) and that using clinical ethics committees to oversee unproven interventions might be a better way to act in people’s best interests when there is a weak evidence base.33

Another ethical issue is that targeting certain groups for experimental vaccines, such as sex workers, gay, bisexual and men-who-have-sex-with-men, can contribute to stigma and discrimination of these groups.

For clinical trials

Aspects of SBS and RCCE should be considered at all stages of clinical trial, such as a cluster RCT, for an experimental vaccine during a disease outbreak; see Figure 1. Each stage requires ongoing monitoring of public responses through community engagement and dialogue, as described in more detail below.34

Stage 1. Trial design and planning during disease outbreaks

Good communication should help a community understand the trial and the reasons why the trialists have taken certain decisions, such as which groups of people are included or excluded from the trial (inclusion/exclusion criteria) and how the people are selected to receive the vaccine (randomisation).

Conducting rapid formative SBS research on acceptability (of the trial and the vaccine) with participants and the wider community can help with understanding local people’s beliefs, motivations, views and emotions (including hopes, expectations, fears and concerns) about the disease as well as the experimental vaccine. It is also important to understand the influence of past experiences of interventions and research (external or government-led) as well as media and social media representations and portrayals of historical deployment of experimental pharmaceutical products. The SBS research can help to ensure that community engagement strategies and trial design are informed by evidence and community needs.

Stakeholder power mapping can identify trusted and influential authorities or gender and power dynamics. The mapping can help researchers build trust with community and religious leaders, local facilitators and moral authorities, and identify key influencers within communities. Power mapping can help reconcile competing interests for how benefits and risks are shared. Identifying these groups (e.g., community and religious leaders, local facilitators and other moral authorities) and dynamics can help build trust vital to ensure relevance and accessibility.35

Trial teams should draw on best practice and refer to the WHO’s ‘Good participatory practice guidelines for trials of emerging (and re-emerging) pathogens…’. These guidelines include the foundational principles of respect, fairness, integrity, transparency, accountability and autonomy, which underpin partnerships among trial stakeholders in situations of crisis.36

Stage 2. Research and ethical approval

In seeking regulatory approval for vaccines, the ethics of both a trial and roll-out must balance benefits and risks. Policymakers can be informed of perceived benefits and risks through patient and public involvement and engagement groups to integrate participant and community perspectives on aspects of the study design (e.g., the protocol, for informed consent processes, reimbursement, follow-up and study exit). Scientists can feed these perspectives into ethical protocols on informed consent, reimbursement, specific procedures and recruitment.

Stage 3. Testing

While a trial is in progress, there is a need to develop RCCE strategies that are well-aligned with the local context and priorities. It is critical that the strategies for RCCE develop tailored messaging and framing that are open and transparent, including via mass or social media communication. For example, during the COVID-19 pandemic, the WHO’s health promotion materials were framed to highlight the gains of health-affirming behaviours rather than the risks of not vaccinating.34 This approach has been shown to be more effective at engaging end users.34 RCCE strategies should prioritise influential groups (e.g., healthcare workers) and vulnerable groups (e.g., children and pregnant women) who may have additional anxieties.

Researchers should be aware of local priorities. Social and behavioural science research should aim to understand local communities’ perceptions, knowledge, anxieties, ideas of risk, beliefs and emotions, all of which have been shown to play a part in acceptability of vaccines.37 Formative research can help inform strategies to increase the acceptance and uptake of vaccines, especially when focused on specific groups.38 The trial and its community engagement approaches should align with relevant local knowledge including about illness, disease, conceptions of health and health-seeking behaviours.

Communication strategies should use locally spoken languages and culturally sensitive approaches. These strategies should also be sensitive to the impact of the disease outbreak and the trial on local health systems, and they should consider potential impacts on health services.

Ongoing monitoring of public responses to experimental vaccines

A dynamic epidemiological situation will require ongoing dialogue and monitoring led by RCCE specialists to identify accepted channels of communication. By conducting ongoing operational research, RCCE specialists can ensure that channels with the greatest reach and established trust are utilised throughout the trial period and beyond. It is also important to collect data on a continuous basis to track rumours, identify and address misinformation, and monitor changing community perspectives relating to vaccine concerns, requirements and views about the trial. For example, the WHO has an Emergency Communications Network of trained experts who can be deployed to provide on-site communication assistance for public health emergencies.

Recent experiences of using experimental vaccines health emergencies

Most of the vaccines rolled out for a public health emergency of international concern (PHEIC) since 2009 have been experimental. Of the seven disease outbreaks declared as a PHEIC by the WHO, only polio (in 2024) was vaccinated against using routine mass immunisation.39 Since 2009, the following PHEICs have led to the introduction of vaccines that required development or repurposing: H1N1 (or swine flu) in 2009, Zika virus disease in 2016, Ebola virus disease in 2014 and 2019, COVID-19 in 2020, Marburg virus disease in 2024, and mpox in 2022 and 2024. For the 2014 Ebola virus disease epidemic and 2016 Zika epidemic, vaccines were not developed in time to be tested and rolled out as licensed products during the epidemics.

Experimental vaccines have a long history of being used during health emergencies in colonial and wartime contexts. However, in more recent years, the role of experimental vaccines has again become more established. Experiences with Ebola virus disease and COVID-19 provide rich insights into the choices faced about research design and vaccine roll-out as well as the implications for SBS and RCCE interventions. These health emergencies, which were characterised by increased uncertainty and circulating misinformation, bring another level of complexity to processes of financing, ethical review and setting standards for the collection of evidence. We explore these two examples of health emergencies in more detail below.

Ebola virus disease

At the beginning of the 2014 to 2016 West African Ebola virus disease epidemic, vaccine trials were deemed inappropriate by international organisations, particularly the WHO Ethics Working Group, even though experimental vaccines were available. The prevailing view was that all resources should be directed towards alleviating suffering rather than conducting research, and that the ethical and practical challenges of conducting research in the fragile health systems of affected countries would be insurmountable. There were fears among some responders that the public would not be able to understand key aspects of trials, such as the risks of adverse events and would not accept vaccines. At the time, Ebola virus disease vaccines had previously only been tested in preclinical studies with nonhuman primates.

Initial opposition to the use of experimental vaccines – as part of an emergency roll-out in trials by the WHO and some nongovernmental organisations providing care on the ground – was centred around concerns that untested medical products would increase the difficulties that healthcare workers faced, particularly in relation to rising mistrust, the circulation of conspiracy theories and the threat of violence. However, the possibility of experimental vaccine use reemerged after accusations of unequal treatment of infected African healthcare workers who were unable to access lifesaving interventions, while volunteers from the USA were given experimental therapeutics.40

Ethical framework and introduction of experimental vaccines

In 2014, the WHO convened an ad hoc expert panel to provide guidance on the ethical acceptability of experimental treatments, diagnostics and vaccines in response to the Ebola virus disease epidemic. The panel deemed the use of these interventions acceptable because of the high mortality rate and transmission intensity associated with the Ebola virus disease outbreak.41 Previously, experimental interventions – including vaccines – had typically been provided when there was no other suitable option and a clinical trial was not possible. The WHO subsequently issued the MEURI ethical framework to provide guidance on the use of interventions outside clinical trials during public health emergencies.42

The MEURI framework sets out criteria for experimental use of pharmaceutical interventions, including the justification for their use, what sort of ethical and regulatory oversight would be needed, the consent process and how evidence could be collected. MEURI is intended for use when medical research is impracticable but there is a need to systematically gather data on safety and efficacy.33 It should be noted that consideration of the ethics of clinical research in public health emergencies had already begun during the severe acute respiratory syndrome (SARS) coronavirus pandemic in 2003 and following the H1N1 swine flu pandemic in 2009.43

Merck’s rVSV-ZEBOV Ebola virus disease vaccine was first introduced on an emergency basis using a ring vaccination strategy to vaccinate nearly 800 people in Guinea in March 2016. The vaccine was also rolled-out in studies examining antibody responses in 477 individuals in Liberia and approximately 500 individuals in Sierra Leone.44 It was later used in the DRC during the 2018 outbreak in Équateur province and in the 2018 to 2020 outbreak in Kivu, with over 90,000 people vaccinated in total.45 Only in 2019 was the vaccine licensed in Europe and the USA, and in 2020 it was licenced in the DRC, followed by Burundi, Ghana, Zambia and Guinea after prequalification by the WHO.46

Prequalification by the WHO is provided following an evaluation by a team of assessors of comprehensive data regarding quality, safety and efficacy (e.g., ingredients, finished product, testing/trial results, inspection of manufacturing sites) submitted by the manufacturer.47 Trials can also continue (after an experimental vaccine introduction) to collect data and evidence about immunity or protection conferred by a vaccine. For example, the Partnership for Research on Ebola Vaccination trial (PREVAC, NCT02876328) demonstrated that immunity from three different Ebola vaccines lasts for up to five years after vaccination.48

For this trial, the French, African-based non-governmental organisation ‘The Alliance for International Medical Action’ (ALIMA) facilitated volunteer recruitment and ensured follow-up throughout the study through the use of 60 community facilitators and community-focused data collection exercises.49 The organisation, ALIMA, also helped to establish community-based treatment centres for Ebola virus disease and ran re-integration programmes with survivors as part of continued control efforts in communities. Such efforts have been shown to help with community adherence to disease control activities (e.g., contact tracing) for case detection and management.49

Best practices for communication and community engagement

Experimental vaccines were introduced both within and outside of trials first in Guinea during the 2014-2016 West African Ebola virus disease epidemic. In emergency committee meetings held in the WHO in 2014, community engagement and social mobilisation were identified as a priority for successful clinical trials and vaccination campaigns after local resistance to the emergency response that had already taken place. The WHO’s Strategic Advisory Group of Experts on Immunization subsequently approved the Merck vaccine for use under an expanded access/compassionate use protocol, and Merck vaccines were introduced in DRC during the 2018-2020 outbreak using a ring vaccination strategy.

Many of the experimental Ebola virus disease vaccine usage within trials and outside of trial settings targeted specific individuals or groups (e.g., healthcare workers) and used different approaches for communication and community engagement. These trials have now become a reference point for the evidentiary needs, data sharing protocols and regulatory adjustments necessary for research in public health emergencies.50 Insights from the trials included the importance of taking steps to retain participants, provide dedicated community engagement resources and use targeted communication to share information. Specifically, trials in different countries involved various approaches to community engagement and communication:

  • Using participant trackers – local people employed to engage in ongoing conversations about daily experiences of being in this trial in Liberia – highlighted the need for interpersonal, local and face-to-face communication.51 The trial collected crucial information to determine the names, locations and contact details of participants, but the potential intrusiveness of this intervention was not assessed.
  • Efforts to collect and analyse rumours by the non-governmental organisation ‘Internews’ in Liberia showed people were concerned about government interventions, which included vaccination.
  • The ‘Ebola Ça Suffit!’ trial in Guinea has been held up as a model of community engagement and social mobilisation, although commentators noted the need for more widespread ‘bottom-up’ approaches to include local people in planning and implementation as well as listening and responding to community needs.50
  • A dedicated community liaison team was set up to manage messaging and communication, conditions for participation and informed consent in a trial in Sierra Leone. The team worked closely with trial researchers and social scientists and concentrated on the direct public engagement about the trial and what participation involves through community- and household-level meetings alongside community leaders.52
  • For another trial in Sierra Leone, a dedicated 24-hour hotline was available for questions or concerns, and information-sharing meetings were held for potential participants (healthcare workers) and the wider health workforce.53

Building trust

Several trials have grappled with issues associated with a loss of trust by participants and the wider public. As an example, an Ebola virus disease vaccine trial (DRC-EB-001), which tested two doses of the Janssen vaccine, was conducted during the COVID-19 pandemic in the DRC. The trial faced challenges of rumours about trial procedures (e.g., concerns that the Ebola virus disease vaccine would be replaced by a COVID-19 vaccine) and reduced confidence when protocol changes were made mid-trial (to delay the second vaccine dose) due to the COVID-19 pandemic.54

These challenges highlighted the need to consider the effect of multiple concurrent disease outbreaks on a trial. Even where participants sought out the second dose, circulating rumours regarding vaccine safety may have caused distress.54 The COVID-19 pandemic also provoked wider political economy debates about healthcare access, spanning ineffective local governance, global inequality and Western biomedical colonialism.54

COVID-19

During the COVID-19 pandemic, criticisms arose about poor government communication and the nature and transparency of policy decisions. These criticisms led to a fall in trust and confidence in government decision-making. However, potential new avenues for communication have also been highlighted, such as using contact tracers for health communication and to generate knowledge about how to send and frame messages or providing health information to inform outbreak response.55 Further, COVID-19 vaccine and treatment trials were highly politicised in several countries. Some of the issues that arose around COVID-19 vaccine testing and roll-out are described below.

Politicisation

In South Africa, healthcare workers participated in a trial of the Janssen COVID-19 vaccine in February 2021 while the licencing process took place; this trial was also called the Sisonke Programme (VAC31518COV3012). The trust in the trial deteriorated after news broke of government corruption: politically connected individuals were awarded contracts for the provision of personal protective equipment tenders and for an illegitimate communications contract with a company called Digital Vibes.56 Studies have shown that lack of trust in the government due to corruption negatively affected vaccine hesitancy in the country.57

The pandemic saw an increase in both the authorised and unauthorised emergency use of unproven clinical interventions outside of clinical trials. Monitoring and control of such interventions are still needed even if it is determined that the benefits outweigh the risks. Ivermectin and hydroxychloroquine are two examples: there were concerns about their efficacy because evidence was lacking, and their risk-benefit profiles were substandard or mixed. Both drugs were promoted by powerful voices and portrayed in highly emotive terms, which led to an increase in demand. In response, the WHO published an updated version of the MEURI framework to guide the use of such interventions.42

Governments also acted in ways that reduced confidence in vaccines. In Brazil, the testing and roll-out of experimental COVID-19 vaccines were undermined by government actions. A trial of the Chinese CoronaVac vaccine in the country was suspended after a volunteer experienced a serious adverse event, later shown to be unrelated to the vaccine. The then President Jair Bolsonaro claimed a ‘victory’ while also promoting untested and unproven treatments.58

For example, an early treatment trial called ‘Prevent Senior’ was conducted by a private health insurance company using drugs such as hydroxychloroquine and azithromycin. This trial gained government support and formed part of government policy that promoted the use of ineffective drugs.59 This trial was later shown to be unethical by the Brazilian Federal Senate.59

Regulatory processes and data management

The regulatory environment for experimental vaccines has changed substantially since the COVID-19 pandemic with expedited regulatory processes; increased coverage, availability and dissemination of information and data via media and social media; and increased levels of public interest and scrutiny, where public audiences are highly engaged but often polarised. This backdrop presents both major challenges and opportunities for public openness, transparency, engagement and dialogue.

During the pandemic, many countries introduced new forms of regulatory processes and data management for vaccine testing and roll-out. For example, ultra-rapid protocol reviews with regulatory bodies for clinical trials were conducted within much shorter time frames than was typical before the pandemic.

Further, several countries established rapid trial enrolment processes to aid recruitment through efforts such as improved participant databases. National and international participant databases can help streamline processes to identify suitable study subjects quickly and facilitate enrolment in clinical trials. These databases can also help address ethical and safety concerns by helping to ensure that informed consent has been implemented properly, and they can minimise risk by checking participants have not enrolled in multiple trials.60

Ethicists have argued that similar registries should also be established in low- and middle-income countries (LMICs) to help minimise the risk of exploitation, exposure to risk and ensure genuine informed consent.60 However, general concerns have also been raised regarding expediated regulatory arrangements and problems with a lack of data availability, especially in LMICs.61

Trial and vaccine legitimacy

The high demand for COVID-19 vaccines had consequences for ensuring legitimacy of trials and vaccines. Fake trials have meant governments had to contend with scams attempting to enrol volunteers to extract money, and some countries were compelled to issue guidance on how to differentiate between a real or fake clinical trial.62

Further, the WHO flagged the rise of fake vaccines in India and Uganda after identifying counterfeit versions of Covishield (India’s primary COVID-19 vaccine) being marketed through spam email and social media in both countries.63 Conspiracies and rumours about the safety and risk of experimental COVID-19 vaccines presented further challenges to public health communication strategies.

The COVID-19 pandemic highlighted the stark inequities in vaccine trial locations that exclude LMICs.64 COVID-19 vaccination trials spurred a debate critiquing Western-led clinical research and barriers to accessing health interventions in LMICs. At the same time, recurrent concerns about LMICs being ‘testing grounds’ also came to the surface. One high-profile controversy involved French doctors suggesting COVID-19 treatments be tested first in Africa, which was critiqued as racist.65

Inequity in vaccine supply, roll-out and access was also a major issue during the pandemic. LMICs contended with higher-income countries’ vaccine nationalism in which supplies were often hoarded. This nationalism highlighted the need to build vaccine and vaccination capacity by strengthening health systems and developing regional manufacturing hubs.66

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Authors: Samantha Vanderslott (University of Oxford) and Hana Rohan (independent consultant).

Acknowledgements: This brief was reviewed by Megan Schmidt-Sane and Juliet Bedford (Anthrologica). The brief is the responsibility of the Social Science in Humanitarian Action Platform. Editorial support provided by Harriet MacLehose and Georgina Roche. This brief is the responsibility of SSHAP.

Suggested citation: Vanderslott, S. and Rohan, H. (2025). Key considerations for introducing experimental vaccines during health emergencies. Social Science in Humanitarian Action (SSHAP). www.doi.org/10.19088/SSHAP.2025.024

Published by the Institute of Development Studies: May 2025.

Copyright: © Institute of Development Studies 2025. This is an Open Access paper distributed under the terms of the Creative Commons Attribution 4.0 International licence (CC BY 4.0). Except where otherwise stated, this permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited and any modifications or adaptations are indicated.

Contact: If you have a direct request concerning the brief, tools, additional technical expertise or remote analysis, or should you like to be considered for the network of advisers, please contact the Social Science in Humanitarian Action Platform by emailing Annie Lowden ([email protected]) or Juliet Bedford ([email protected]).

About SSHAP: The Social Science in Humanitarian Action (SSHAP) is a partnership between the Institute of Development Studies, Anthrologica , CRCF Senegal, Gulu University, Le Groupe d’Etudes sur les Conflits et la Sécurité Humaine (GEC-SH), the London School of Hygiene and Tropical Medicine, the Sierra Leone Urban Research Centre, University of Ibadan, and the University of Juba. This work was supported by the UK Foreign, Commonwealth & Development Office (FCDO) and Wellcome 225449/Z/22/Z. The views expressed are those of the authors and do not necessarily reflect those of the funders, or the views or policies of the project partners.

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